How to fix irregular cross section and shape-stretching while curving a mesh?
You could do it this way:


Create a torus with 6 Major Segments. Rotate it 90° on the X axis and 30° on the Y axis. Apply the rotation with ctrlA.
Duplicate it and keep a half somewhere.
Cut the 2 extremities with the knife (K to activate, Z to cut through, C to cut perpendicularly), separate in the middle with V, move one half and create an X.
Give your shape an Array modifier with a Count of 7, activate the Merge and First Last options.
Give it a Simple Deform modifier / Bend mode, with the angle you want, for example 280° if your final shape is not closed.
As you will want to smooth it with a Subdivision Surface modifier, add some edge loops to your mesh to sharp the edges.
Give it a Subdivision Surface modifier, smooth it.
Keep a copy of your object somewhere. Apply the Array and Simple Deform modifiers on the original.
Bring back the half torus you've created at the beginning and stick it to each extremity of the shape with the help of the Snap option / Vertex mode and Automatically Merge Vertices option.
Go in Edit mode, select all and W > Remove Doubles.